Ethernet

Ethernet is a family of computer networking technologies for local area networks (LANs). Ethernet was developed at Xerox PARC between 1973 and 1974 by Robert Metcalfe. Metcalfe developed the physical method of cabling that connected devices on the Ethernet as well as the standards that governed communication on the cable. Ethernet has since become the most popular and most widely deployed network technology in the world.  Ethernet facilitates communication over a single cable shared by all devices on the network. Once a device is attached to this cable, it had the ability to communicate with any other attached device. This allows the network to expand to accommodate new devices without requiring any modification to those devices already on the network.

Ethernet Topology:

The topology of an Ethernet network has changed out of necessity over the years as the networking technologies have evolved. Where in the 90's Bus topology was very popular today this has made way for what is called Star Topology. In Bus topology the whole LAN was considered one big collision domain which meant only one device could transmit data at any one point in time. Today's Star Topology, or switched ethernet, splits any LAN up into segments which runs its own separate ethernet protocol, which allows devices to transmit simultaneously either in duplex or half duplex.

Half Duplex:

Bi-directional transmission but not at the same time using one collision domain.

Duplex:

Bi-directional transmission at the same time using two collision domains.
Never a collision when devices are connected using full duplex Ethernet switch.


Advantages of Star topology:

• Easy to install and wire
• No disruptions to the network when connecting or removing devices
• Easy to detect faults and remove parts

Disadvantages of Star topology:

• Requires more cable length than bus topology
• If switch fails, devices attached are disabled and cannot participate in network communication
• Expensive due to cost of switches and longer cables

Ethernet Media types:

Ethernet Medium Access Control:

Ethernet is a broadcast medium where in one device is a sender while every other device receives the data. Each device listens to everything going up and down the wire, identifies the start of the frame, and copies the data on wire into a buffer. Here it examines destination MAC address to see if it is for that device and if yes it continues reading the rest of the frame otherwise it drops the frame. (CSMA/CD)